The return justified Sir Alex
Ferguson's decision to spend £24million on the 29-year-old last summer
in the wake of City winning the title last term.

And O'Neill can see why. 'Robin van
Persie was a great purchase,' said O'Neill. 'It means Manchester United
are capable of scoring goals because Wayne Rooney is a top quality
player as well.

'Whilst their main players stay fit Manchester United are capable of winning the league.'

O'Neill certainly wished some of the
criticisms that have been levelled against United could be said of his
own team now that United will definitely be top on Christmas Day.

Tom Cleverley's first Premier League
goal at Old Trafford was followed by Wayne Rooney's fifth in four games
to put the hosts in control, before Frazier Campbell grabbed a
consolation against his former club.

'People keep saying we are weak in midfield but these guys are very good players,' said Sir Alex Ferguson.

'Sometimes it gives me a little
problem selecting the right two, although today was simple because
(Michael) Carrick and Cleverley deserved to play after their performance
(against Manchester City) last week.'

Cleverley is making an impact in the
Paul Scholes role, with Ferguson admitting he should be scoring more
often after taking his overall United tally to three.

'Tom has goals in him,' said Ferguson. 'As a younger player he always had a goal in him.

'He has got me three this season and I really do expect more from him because he is a nice finisher.'

Scoring streak: Wayne Rooney netted his fifth goal in three Premier League games

Perhaps the most significant aspect of the day was Nemanja Vidic's return from knee surgery.

The Serbian has made just 14
appearances since August 2011 and Ferguson knows what a vital
contribution he could make in the months ahead.

'It will take him a bit of time but that is a start,' he said. 'He is a warrior and he is our captain.

Rising high: Fraizer Campbell nods home against his former club to hit Sunderland's consolation goal

'He always battles for you and sticks his head on that ball in the penalty area.

'That is what he is great at.'

Ferguson confirmed defender Rafael
had missed only his second Premier League game of the season with a
tight hamstring, which was also the complaint that forced Michael
Carrick off at half-time.

O'Neill had his own injury woes after losing top scorer Steven Fletcher at the break.

Back in action: Nemanja Vidic made a welcome return to the heart of Manchester United's defence - but the Serb could not prevent Campbell's consolation strike

'Steven hurt his back in the warm-up
before the game,' he said. 'He twisted it in some way and it was causing
him a few problems.

'It got more painful in the last 10 minutes of the first half and he couldn't continue.'

O'Neill does not know how long
Fletcher will be out of action, although clearly any injuries are a
major blow to a club only a point above the drop zone and with an
already weak squad.

Knockout: Mignolet and Titus Bramble struggle to contain Patrice Evra

'We would have to be seriously
looking to try to strengthen our side,' said the Irishman. 'You only
have to have look at the back of the programme to see that we don't have
great numerical strength.

'But you are going to get injuries and suspensions. It is up to us to cope with them.

Close control: Van Persie receives a pass at Old Trafford

'Today was going to be hard enough without giving a couple of poor goals away.

'But there is still a decent spirit about us.

'We lack many things in the game but the spirit is still there and has not been broken.'